Leave the Driving to It

An Abundance of Caution

There’s one prediction about driverless cars that I can make with confidence: If millions of them ever roam the public highways, they will be far safer than cars driven by people. My confidence in this assertion does not derive from mere faith in technology. It’s just that if robotic drivers were as dangerous as human ones, then computer-controlled cars would never be allowed on the roads. We hold our machines to a higher standard than ourselves.

Over the past decade, the number of auto accidents in the United States—counting only those serious enough to be reported to the police—has been running at about six million a year. Those accidents kill about 40,000 people and injure well over two million more. Estimates of the economic impact are in the neighborhood of $200 billion. Much of that cost is shared among car owners through premiums for auto insurance.

This safety record certainly leaves ample room for improvement. An appropriate goal for automated vehicles might be to reduce highway carnage to the same order of magnitude experienced in other modes of transport, such as railroads and commercial aviation. That would mean bringing road fatalities down to roughly 1 percent of their current level—from 40,000 deaths per year to 400. (In terms of deaths per passenger mile, cars would then be the safest of all vehicles.)

Could automation achieve such a hundredfold improvement? Taking the controls out of human hands would eliminate several major causes of crashes: drivers who are asleep, inebriated, impatient, inattentive, overconfident, inexperienced. Unfortunately, computer drivers have foibles of their own; at the moment, they cannot even equal human performance, much less surpass it. I believe these failings can be overcome (and I’ll explain how below). But for now let’s just make the assumption that car travel can indeed be made safe, and examine the consequences.

Among young people in the United States, auto accidents are the leading cause of death; between ages 15 and 24, a third of all deaths happen on the road. For this age group, then, safer cars would have a noticeable demographic impact. The financial impact would also be significant—saving $200 billion a year in accident losses, shutting down a $200 billion industry that repairs smashed cars and bodies.

If accidents become rare enough, one would expect to see changes in attitudes and behavior, and perhaps in the design of vehicles. Current custom insists that we always buckle our shoulder harness and strap down the children in the back seat, as if every trip to the grocery store might end with a wreck—as indeed it might. No such precautions are taken on trains, subways, trolleys and buses. As accident rates fall, perhaps we would relax our vigilance in the car as well. And if the driver gradually becomes just another passenger, the interior of the automobile could look less like a padded cell or an airplane cockpit and more like an office, a theater, a café or even a bedroom.

A 99-percent improvement in safety will still leave tens of thousands of auto accidents every year, which may require new legal and financial mechanisms for compensating victims. Most collisions today are attributed to driver error rather than a defect or malfunction in the vehicle. When the vehicle is the driver, this distinction is no longer meaningful. Car manufacturers might be held liable for a larger share of the accidents—a responsibility they are certain to resist. (A legal analysis by Nidhi Kalra and her colleagues at the RAND Corporation suggests this problem is not insuperable.)

The kinds of accidents caused by car-driving computers might be quite different from common human goofs. Of special concern is the possibility of a design flaw in hardware or software that could affect many cars the same way. It’s easy to imagine a scenario in which one car after another follows exactly the same trajectory off a cliff.

Another essential point is that safety has to be balanced against reliability and robustness. Accidents can be reduced to near zero by adopting sufficiently conservative rules of operation. But nobody wants a car that pulls off the road and shuts down when the first snowflake falls.